Battery charge balancing system having parallel switched energy storage elements

• US 6,064,178 A
• Filed: 05/07/1998
• Issued: 05/16/2000
• Est. Priority Date: 05/07/1998
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Ford Motor Company
• Inventors: Miller, David Lowell
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/073,943
• Time in Patent Office: 740 Days
• Field of Search: 320/116, 320/117, 320/118, 320/119, 320/120, 320/122, 320/126, 320/127, 320/128, 320/137
• US Class Current: 320/117
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0018 using separate charge circuits
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A method for balancing charge of a plurality of series-connected batteries includes alternately coupling each of a plurality of energy storage circuits across a respective one of the batteries and in parallel with each other. A charge balancing system comprises a plurality of series connected batteries and a plurality of energy storage circuits. The system also includes switching circuitry for alternately connecting each energy storage circuit across a respective one of the batteries and in parallel with each other. The switching circuitry can also be controlled to couple a plurality of the energy storage circuits across a relatively-highly-charged battery and then across a relatively-weakly-charged battery.

Claims

1. A method for balancing charge of a plurality of series-connected batteries, said method comprising:

(a) coupling each of a plurality of energy storage circuits across a respective one of said batteries;

(b) coupling said plurality of energy-storage circuits in parallel with one another and across none of said batteries; and

alternately repeating steps (a) and (b).

2. A method as recited in claim 1, wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) at a predetermined rate.

3. A method as recited in claim 1, further comprising measuring variables representing relatives state of charge of said batteries;

wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) at a rate which is a function of charge imbalance among said batteries.

4. A method as recited in claim 1, wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) when said batteries are being discharged to a device external to said plurality of series-connected batteries and said plurality of energy storage circuits.

5. A method as recited in claim 1, wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) when said batteries are being discharged to provide power to an electric motor.

6. A method as recited in claim 1, wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) when said batteries are being charged from a device external to said plurality of series-connected batteries and said plurality of energy storage circuits.

7. A method as recited in claim 1, wherein alternately repeating steps (a) and (b) further comprises alternately repeating steps (a) and (b) when said batteries are neither being charged nor discharged.

8. A system for balancing charge to a plurality of batteries, said system comprising:

a plurality of series connected batteries;

a plurality of energy storage circuits;

means for alternately connecting each said energy storage circuit across a respective one of said batteries and in parallel with each other across none of said batteries.

9. A system as recited in claim 8, further comprising means for measuring voltages across each of said batteries;

wherein said alternate connection means further comprises means for performing said alternate connections at a rate which is a function of said measured voltages.

10. A system as recited in claim 8, wherein said alternate connection means further comprises means for performing said alternate connections at a predetermined rate.

11. A system as recited in claim 8, wherein said alternate connection means further comprises means for performing said alternate connections when said batteries are being charged from a charger external to said system.

12. A method as recited in claim 8, wherein said alternate connection means further comprises means for performing said alternate connections when said batteries are being discharged to a device external to said plurality of series-connected batteries and said plurality of energy storage circuits.

13. A system as recited in claim 8, further comprising an electric motor, and wherein said alternate connection means further comprises means for performing said alternate connections when said batteries are being discharged to provide power to said motor.

14. A system as recited in claim 8, wherein said alternate connection means further comprises means for performing said alternate connections when said batteries are being neither charged nor discharged.

15. A battery charge balancing system comprising:

a plurality of series-connected batteries each having a first and second terminal;

a plurality of switching circuits equal in number to said plurality of batteries, each said switching circuit coupled to a respective one of said batteries and further comprising;

an energy storage circuit having a first and second termination;

a first switch coupled between said first termination of said energy storage circuit and the first terminal of said respective battery;

a second switch coupled between said second termination of said energy storage circuit and the second terminal of said respective battery;

a third switch coupled between said first termination of said energy storage circuit and a first common point;

a fourth switch coupled between said second termination of said energy storage circuit and a second common point;

wherein said first common points of said switching circuits are coupled together and said second common points of said switching circuits are coupled together.

16. A battery charge balancing system as recited in claim 15, further comprising means for controlling said switching circuits to alternately connect said energy storage circuits across their respective batteries and in parallel with each other.

17. A battery charge balancing system as recited in claim 15, further comprising means for controlling said switching circuits to alternately connect a plurality of said energy storage circuits across a first said battery and then across a second said battery, to transfer charge from said first battery to said second battery.